The invention relates to a method and apparatus for producing short-lived reactive species in a rapid thermal processing (RTP) system.
RTP systems are employed in semiconductor chip fabrication to create, chemically alter, or etch surface structures on semiconductor wafers. In one type of system, an RTP chamber includes a gas manifold, sometimes referred to as a gas showerhead, positioned above the surface of the wafer to provide a flow of a process gas to the wafer surface. Radiant energy from a heat lamp array passes through the manifold, which can be made of transparent quartz, to heat the wafer during processing. Spent process gas can be pumped out through a vacuum port of the chamber.
Completely replacing one process gas with another one typically takes several minutes with a conventional gas showerhead system. For this reason, it is very difficult to rapidly switch from one type of process to another at the surface of the wafer, such as is desirable in creating very thin layers or structures on the wafer surface. Some RTP processes employ highly reactive species, such as atomic species. In conventional systems, these species are created outside the RTP system, for example, with an electric discharge. The reactive species created by such methods must travel long paths to reach the wafer with conventional showerhead systems. Atomic species can also be created with an electric discharge within the RTP chamber, but employing an electric discharge close to the wafer surface also creates a plasma that can be detrimental to the semiconductor devices being formed on the wafer.